Since John is using a RD75, so time to put a RD75 on an available 17" flat baffle, not wide enough for the low frequencies that this driver is capable of reproducing, but as stated, it was available. You will notice some quarter wave dipole baffle cancellation. All circumstances are similar to the previous plots in the "bounce" interlude, no crossovers, no equalisation.
Microphone is at 1 meter above floor level. There is definitely a difference here, the magnitude of the peaks and dips is changing but not the location as opposed to the monopole plots where magnitude and location changed. If we assume for a second that the flat line is at -10 dB then there is definitely a 6 dB bump at approximately 400 Hz. At two meter, besides the 400 Hz bump, a response +/- 3dB from 600 Hz to 16 kHz.
Raising the microphone to 1.5 meter level produced following results:
Bumps and dips with different magnitude, similar location, "interpolated" in a different way, result of relationship between direct and indirect sound.